An outboard marine motor typically includes an internal combustion engine, a propeller which is powered by the engine and produces a propelling force, and a skeg formed in a lower part thereof to afford directional stability. The outboard marine motor is typically attached to a transom board of a boat via a mounting fixture which includes a vertical hinge shaft so that the outboard marine motor can be pivoted around the hinge shaft in either direction. The pivoting movement of the outboard marine motor causes the direction of the propeller and skeg to be changed accordingly, and this provides a steering action of the boat.
Therefore, the steering action of the boat requires an upper part of the outboard marine motor to be turned in a corresponding manner. The upper part of the marine motor is enlarged, in particular in the lateral dimension thereof, as compared with a lower part thereof because the engine is placed in the upper part thereof. Therefore, to ensure a large steering angle, there is a need to avoid any interference between the outboard marine motor and adjoining part of the boat.
It is proposed in Japanese patent laid open publication No. 63-97489 to place the engine inside the boat and a propulsion system including a propeller outside the boat. It allows the propulsion system to be turned around the pivot shaft to a desired angle without difficulty, but the engine limits the available space of the boat. This is not acceptable particularly in small boats.
When the outboard marine motor is steered, a significant force is required to maintain the steering angle owing to the resistance of water applied to the skeg and other parts of the outboard marine motor. This creates a need for a relatively large power actuator.
Japanese patent laid open publication 2006-264523 discloses an outboard marine motor that is incorporated with a hydraulic actuator to steer the outboard marine motor. This allows the outboard marine motor to be steered without any manual effort, and simplifies the remote control arrangement for steering the outboard marine motor, but has the disadvantage that the hydraulic actuator must be placed in a part of the boat on which the outboard marine motor is mounted. This is not desirable in small boats that have limited available space. Also, this complicates the structure of the mounting fixture that is used to mount the outboard marine motor on the boat.